The invention relates to a fluid filter of the type having assembled parts and a filter disposed between such parts.
German Patent 31 23 269 discloses a filter for fluids in which the filter body is a folded sheet with a substantially rectangular outline and a housing is provided which is formed of two halves and encloses the filter body. Such filters serve for the filtration of transmission oil or fuels and are intended to achieve a high filtering action over a long period of time, in a very compact form.
In the known filter element one housing half is made of sheet metal, while the other housing half is a one-piece pressure-cast piece of fiber-reinforced polyamide. When this filter is assembled, the sheet metal is crimped onto the margin of the polyamide half, resulting in the permanent fastening together of the two housing halves.
In European Patent 03 96 385 A2 a filter for an automatic transmission is disclosed. It consists of two plastic housing parts. Between them is the filter material. The two plastic housing parts are joined together by friction welding at their peripheral surfaces.
A disadvantage in the use of friction welding is the fact that manufacturing inaccuracies impair the effect of the friction welding, i.e., there is the danger that part of the peripheral welding surface that had less than the best contact is welded imperfectly or not at all. Precisely in a filter of this kind, however, a reliable sealing of the filter element is essential, so that the vacuum prevailing in the filter will not be able to suck any air into the filter through the housing seam when the oil level is low or the vehicle is rounding a curve.
Even in the case of the filter referred to in German Patent 31 23 269 with the crimped margin there is the danger of leaks around the edges.
Another disadvantage of the known filter for fluids is to be seen in the fact that it is not possible to replace the used filter and reuse the housing.